[3.6] bpo-30604: Move co_extra_freefuncs to interpreter state to avoid crashes in threads (#2015)

* Move co_extra_freefuncs to interpreter state to avoid crashes in
multi-threaded scenarios involving deletion of code objects

* Don't require that extra be zero initialized

* Build test list instead of defining empty test class

* Ensure extra is always assigned on success

* Keep the old fields in the thread state object, just don't use them
Add new linked list of code extra objects on a per-interpreter basis
  so that interpreter state size isn't changed

* Rename __PyCodeExtraState_Get and add comment about it going away in 3.7
Fix sort order of import's in test_code.py

* Remove an extraneous space

* Remove docstrings for comments

* Touch up formatting

* Fix casing of coextra local

* Fix casing of another variable

* Prefix PyCodeExtraState with __ to match C API for getting it

* Update NEWS file for bpo-30604

1 files changed, 17 insertions, 11 deletions

diff --git a/Objects/codeobject.c b/Objects/codeobject.c
index 22c4f85..d38f185 100644
--- a/Objects/codeobject.c
+++ b/Objects/codeobject.c
@@ -411,11 +411,11 @@ static void
 code_dealloc(PyCodeObject *co)
 {
     if (co->co_extra != NULL) {
-        PyThreadState *tstate = PyThreadState_Get();
+        __PyCodeExtraState *state = __PyCodeExtraState_Get();
         _PyCodeObjectExtra *co_extra = co->co_extra;
 
         for (Py_ssize_t i = 0; i < co_extra->ce_size; i++) {
-            freefunc free_extra = tstate->co_extra_freefuncs[i];
+            freefunc free_extra = state->co_extra_freefuncs[i];
 
             if (free_extra != NULL) {
                 free_extra(co_extra->ce_extras[i]);
@@ -825,8 +825,6 @@ _PyCode_CheckLineNumber(PyCodeObject* co, int lasti, PyAddrPair *bounds)
 int
 _PyCode_GetExtra(PyObject *code, Py_ssize_t index, void **extra)
 {
-    assert(*extra == NULL);
-
     if (!PyCode_Check(code)) {
         PyErr_BadInternalCall();
         return -1;
@@ -837,6 +835,7 @@ _PyCode_GetExtra(PyObject *code, Py_ssize_t index, void **extra)
 
 
     if (co_extra == NULL || co_extra->ce_size <= index) {
+        *extra = NULL;
         return 0;
     }
 
@@ -848,10 +847,10 @@ _PyCode_GetExtra(PyObject *code, Py_ssize_t index, void **extra)
 int
 _PyCode_SetExtra(PyObject *code, Py_ssize_t index, void *extra)
 {
-    PyThreadState *tstate = PyThreadState_Get();
+    __PyCodeExtraState *state = __PyCodeExtraState_Get();
 
     if (!PyCode_Check(code) || index < 0 ||
-            index >= tstate->co_extra_user_count) {
+            index >= state->co_extra_user_count) {
         PyErr_BadInternalCall();
         return -1;
     }
@@ -866,13 +865,13 @@ _PyCode_SetExtra(PyObject *code, Py_ssize_t index, void *extra)
         }
 
         co_extra->ce_extras = PyMem_Malloc(
-            tstate->co_extra_user_count * sizeof(void*));
+            state->co_extra_user_count * sizeof(void*));
         if (co_extra->ce_extras == NULL) {
             PyMem_Free(co_extra);
             return -1;
         }
 
-        co_extra->ce_size = tstate->co_extra_user_count;
+        co_extra->ce_size = state->co_extra_user_count;
 
         for (Py_ssize_t i = 0; i < co_extra->ce_size; i++) {
             co_extra->ce_extras[i] = NULL;
@@ -882,20 +881,27 @@ _PyCode_SetExtra(PyObject *code, Py_ssize_t index, void *extra)
     }
     else if (co_extra->ce_size <= index) {
         void** ce_extras = PyMem_Realloc(
-            co_extra->ce_extras, tstate->co_extra_user_count * sizeof(void*));
+            co_extra->ce_extras, state->co_extra_user_count * sizeof(void*));
 
         if (ce_extras == NULL) {
             return -1;
         }
 
         for (Py_ssize_t i = co_extra->ce_size;
-             i < tstate->co_extra_user_count;
+             i < state->co_extra_user_count;
              i++) {
             ce_extras[i] = NULL;
         }
 
         co_extra->ce_extras = ce_extras;
-        co_extra->ce_size = tstate->co_extra_user_count;
+        co_extra->ce_size = state->co_extra_user_count;
+    }
+
+    if (co_extra->ce_extras[index] != NULL) {
+        freefunc free = state->co_extra_freefuncs[index];
+        if (free != NULL) {
+            free(co_extra->ce_extras[index]);
+        }
     }
 
     co_extra->ce_extras[index] = extra;